Compact centrifugal fan

ABSTRACT

The invention relates to a compact centrifugal fan, in which a motor mounting lies on an elastomeric element arranged in a through-opening between the fan housing and the motor mounting, said motor mounting being fixed to the fan housing by means of the elastomeric element.

The invention relates to a centrifugal fan, in particular a gas fan thattransports fuel and air and that comprises a fan housing with a fanwheel arranged in it and with a through opening for running a driveshaft through it, which drive shaft is to be connected to the fan wheel.

Such a centrifugal fans are known from the prior art, for example, fromDE 102 04 037 B4. The construction known from this patent has frequentlyproved itself in practice. Nevertheless, it is desirable to reduce thenumber of parts and to minimize the construction space required for thestructural components arranged on the fan housing. It is especiallyinteresting in a fan construction with laterally arranged electromotorto keep the axial extension along the drive shaft as small as possible.

Given this background the invention has the problem of making availablea more compact centrifugal fan or gas fan with an electromotor arrangedon its side which fan requires fewer structural fixing components and ismore economical. Another aspect is to be able to carry out a tightnesscheck of the centrifugal or gas fan in an easier and more comprehensivemanner.

Furthermore, it should be ensured that the gas fan in accordance withthe invention can be mounted in easy and automated manner. For theoperation of the fan it is to be ensured that the shaft and the fanwheel arranged on it do not oscillate in the axial direction.Furthermore, there is the problem for the fan of the invention ofensuring an improved protection against moisture and a lower thermalstressing of electronic structural control components.

These problems are solved by a pre-fixing centrifugal blower accordingto claim 1 and the following subclaims. Every fan which transports amixture of fuel and air to a burner is to be understood as a gas fan.

It is provided according to the invention that the centrifugal fancomprises a fan housing with a fan wheel arranged in it and a throughopening for running through a drive shaft of an electromotor to beconnected to the fan wheel, wherein the electromotor is arranged on theoutside of the gas fan housing and held by a motor mounting. A part ofthe motor mounting extends through the through opening into the interiorof the fan housing. The motor mounting lies in the mounted state of thefan on an elastomeric element arranged on the through opening betweenthe fan housing and the motor mounting and is fixed by the elastomericelement on the fan housing.

This construction makes it possible to position the motor mounting withthe electromotor arranged on it with a lesser interval than previouslyon the fan housing or the side wall of the fan housing. No additionalfastening means for fixing or decoupling oscillations of the motormounting need to be provided on the fan housing. In the prior art themotor mounting was always fixed with screws on the fan housing, whichare now obsolete due to the fastening by the elastomeric element. Theaxial length or the height of the motor mounting with the electromotorintegrated in it or fastened on it is reduced further by the extensionof a part of the motor mounting through the through opening into theinterior of the fan housing. The area between the outer surface of thefan housing and the surface of the motor mounting facing the fan housingis limited to a minimum according to the invention, wherein the axialsize of the area is determined by the elastomeric element on which thefan housing and the motor mounting rest. The fixing of the motormounting on the elastomeric element takes place via a safety ring thatengages into the motor mounting or via an undercut integrated in themotor mounting. In the case of a solution with a safety ring as well asin a solution with an undercut they are engaged with the elastomericelement in the mounted state and prevent a loosening of the motormounting from the elastomeric element and therefore from the fanhousing. The screwing of the motor mounting to the fan housing, which isnecessary in the prior art, is no longer necessary. The associatedelimination of at least three screws per fan reduces the expense.

Furthermore, it is advantageous according to the invention that the fanhousing used in accordance with the invention has no undercuts forfastening structural components to them so that it can be produced andremoved from the mold with a simple open-close tool.

In an advantageous embodiment the elastomeric element is simultaneouslyconstructed as a seal of the motor mounting opposite an edge of thethrough opening and is arranged directly between the fan housing and themotor mounting. As a result of the sealing function of the elastomericelement between the motor mounting and the fan housing, the only leakagepassage that needs to be checked for tightness is the passage from thefan wheel via the support of the drive shaft to the outside. Therefore,an embodiment of the invention provides that a sealing test edge runningcircumferentially on the outside is provided on the motor mounting. Thesealing test edge is constructed in such a manner that a sealing bellcan be placed over the motor mounting in such a manner that theremaining leakage path is sealed. Therefore, in the case of a tightnesscheck it can also be checked, in contrast to previously used pre-mixinggas fans whether the fan housing wall including the elastic element towhich the motor mounting and therefore indirectly also the electromotorare fastened are also tight.

Furthermore, it is provided in an embodiment of the invention for anespecially compact construction that the part of the motor mountingextending into the interior of the fan housing extends into a free spaceprovided on the fan wheel or a hub of the fan wheel. Therefore, it isnot necessary to maintain a special interval between the fan wheel andthe housing wall in which interval the fixing of the motor mounting iscompleted but rather the fan wheel can be positioned along the innerwall of the fan housing with only a slight slot dimension in order toavoid flow losses.

It is furthermore provided in order to make available an inexpensiveconstruction of the centrifugal fan that can be mounted from one sidethat the drive shaft is supported by a ball bearing and a slidingbearing in the one-part motor mounting. The use of a sliding bearing hasthe advantage that it can be readily mounted and is less expensive. Theinvention provides that the rotor of the electromotor is arrangedbetween the ball bearing and the sliding bearing and that the ballbearing is located axially on the inner side, i.e., closer to thehousing and to the fan wheel. In comparison to the construction knownfrom the prior art the mounting can take place here exclusively from oneside so that it can be automated. The motor mounting comprises a holderon which the ball bearing of the drive shaft rests. Such a holder can beconstructed as a projection in the motor mounting or as acircumferential edge on which the ball bearing is supported. Themounting into the motor mounting takes place in that at first the ballbearing and then the rotor of the electromotor and finally the slidingbearing are pushed or pressed onto the drive shaft. The holder of themotor mounting offers a stop here for the ball bearing and thereforedetermines the axial position of the drive shaft. Alternatively, therotor can be injected onto the shaft.

In an advantageous embodiment the electromotor is constructed as adirect current motor with a rotor arranged on the drive shaft and astator received in the motor mounting. The rotor of the direct currentmotor is fastened in an advantageous embodiment on the drive shaft andthe position of the rotor opposite the stator is offset by one axiallength to the outside, i.e., in the direction away from the fan wheel orthe housing. This off-center arrangement of the rotor in comparison tothe state or in the zero position serves to utilize a magnetic returnforce during the application of the current to press or draw thedriveshaft with the rotor fastened to it into a predetermined direction.The fan wheel itself produces a force in the same direction duringoperation that is, however, dependent for its magnitude on the speed.The off-center arrangement of the rotor opposite the stator in thecurrentless state (zero position) ensures that the shaft with the fanwheel arranged on it does not oscillate in both axial directions duringoperation but rather a defined axial force is always provided in onedirection (in the direction of the central position of the rotor to thestator).

Furthermore, another embodiment of the invention provides that arectangular guide plate is used to control the electromotor. Incomparison to the round guide plates with central recesses for runningthe drive shaft through that are known from the prior art, rectangularguide plates are advantageous since they ensure significantly less wasteof material which reduces the cost. A rectangular guide plate cantherefore be provided according to the invention since it can befastened on the motor mounting radially offset from the drive shaft. Inthis connection the term radially denotes a lateral arrangement relativeto the drive shaft. The fastening of the guide plate on the motormounting can take place, for example, by a clip connection or by someother catch known from the prior art.

An advantageous embodiment provides that the guide plate is arranged onthe motor mounting in a position to the side of or below theelectromotor and which is not influenced by a heat flow caused by theoperation of the electromotor. The inclusion of the pre-mixingcentrifugal or gas fan usually takes place in two alternative positions,vertically or horizontally. This brings it about that the motor mountingand the electromotor fastened to it are arranged horizontally in the onecase and vertically in the other case. Since the heat flow constantlytakes place substantially vertically upward, the guide plate should bearranged either to the side of the flow in the vertical case or belowthe electromotor in the horizontal case. Basically, the thermal load ina side arrangement of the guide plate directly following theelectromotor axially is more advantageous compared to the previousarrangement known from the prior art since the thermal load is less inany case. Furthermore, it is advantageous that a simple connection tothe individual coil bodies of the electromotor via a stamped sheet canbe ensured by a side arrangement.

Furthermore, it is advantageous that in an embodiment of the invention amotor protection cap with a circumferential edge is provided that coversat least the electromotor, the guide plate and the motor mounting andrests with the circumferential edge on the fan housing. This eliminatesthe slot between the motor protection cap and the fan housing wall whichwas previously provided in the prior art and prevents a penetration ofmoisture or other contaminating particles between the fan housing walland the motor protection cap. Therefore, the electromotor is betterprotected. A direct contact is made possible by the fact that the motorprotection cap is fastened directly on the fan housing and not, as inthe state of the art, on the motor mounting. The motor mounting wasconstantly influenced by the vibrations of the electromotor which weretransferred onto the motor protection cap and therefore made a slotnecessary between the fan housing wall and the motor protection cap.This disadvantage is overcome with the direct connection of the motorprotection cap to the fan housing.

Another embodiment provides that air conduction conduits are injectedinto the motor protection cap produced with the injection molding methodand ensure a better removal of the heat generated by the motor. In orderto further the removal of heat, a cooling wing is customarily providedon the drive shaft whose flow cooperates with the air conductionconduits.

All the above-cited features can be combined in all variants in as faras this is technically possible.

Other advantageous further developments of the invention arecharacterized in the subclaims and are presented in detail in thefollowing together with a description of the preferred embodiment of theinvention using the figures. In the figures:

FIG. 1 shows a sectional side view of the centrifugal fan of theinvention;

FIG. 2 shows a detailed view from FIG. 1; and

FIG. 3 shows an exploded view of the parts in FIG. 1 to be mounted.

The figures are of an exemplary, schematic nature and the same referencenumerals refer to the same parts in all views.

FIGS. 1 and 2 shows a pre-mixing centrifugal fan constructed as a gasfan 1 constructed to deliver air and gas to a gas burner via the fanwheel 3. The fan wheel 3 is arranged in a fan housing 2 of which onlythe side cover is shown in FIG. 1. A through opening 4 is provided inthe fan housing 2 through which a drive shaft 5 of an electromotor 6runs and is connected to the fan wheel 3. The electromotor 6 is held bya one-part motor mounting 7 arranged on the outside of the fan housing 2and is fastened on the one-part motor mounting 7. A part 8 of the motormounting 7 extends through the through opening 4 into the interior ofthe fan housing 2 into an area in which the fan wheel 3 is arranged. Anelastomeric element 9 is positioned between the fan housing 2 and themotor mounting 7 on which element the motor mounting 7 rests and bywhich the motor mounting 7 is fixed on the fan housing 2. The fixingtakes place in the view shown by a safety ring 26 that engages into acircumferential groove arranged on the motor mounting 7. The motormounting 7 is therefore directly fixed and tensioned on the fan housing2 by the elastomeric element 9 and the safety ring 26. The elastomericelement 9 serves at the same time as a seal of the motor mounting 7opposite an edge 10 of the through opening 4 so that the single leakagepath from the fan wheel 3 to the outside is the path via the drive shaft5 and its support. In order to make possible a sealing check of the gasfan including the through opening 4 sealed by the elastomeric element 9,a circumferential sealing check edge 11 is provided on the motor carrier7 and can be connected to a sealing bell. The leakage path for the driveshaft 5 and its support is sealed by the sealing bell so that a checkcan be made in a vacuum container whether the tightness of the gas fanincluding the seal is ensured by the elastomeric element 9.

The direct resting of the motor mounting 7 directly on the elastomericelement 9 brings about in addition to the seal a decoupling of theoscillations of the motor mounting 7 with the electromotor 6 arranged onit. The motor mounting 7 moves closer to the fan housing 2 in contrastto explanations from the prior art so that the entire structural spacerequired is reduced in the axial direction of the drive shaft 5. Thepart 8 of the motor mounting 7 which extends into the interior of thefan housing 2 ends in a free space 12 provided in the area of the hub ofthe fan wheel 3. This also makes possible a more compact construction ofthe motor mounting 7 to the fan wheel 3.

The drive shaft 5 is supported twice by a ball bearing 13 and a slidingbearing 14. The ball bearing 13 rests on a holder 15 of the motormounting 7, which holder 15 is constructed as a circumferential edge inthe embodiment shown. The mounting of the structural components of thebearing and of the electromotor 6 takes place on the drive shaft 5exclusively from one side, from above in the embodiment shown. At first,the ball bearing 13 is pressed onto the drive shaft 5, then the rotor 16of the electromotor 6 and finally the sliding bearing 14 is placed on.The rotor 16 can also be injected onto the drive shaft 5. The support ofthe drive shaft 5 takes place from two sides, wherein the ball bearing13 lies axially inward, i.e. closer to the fan wheel 3 and the slidingbearing 14 is located axially outward, i.e. further removed from the fanwheel 3.

The electromotor 6 is a direct current motor in the embodiment accordingto FIGS. 1 and 2 whose is rotor 16 is offset relative to the stator 17by a predetermined axial length X1 toward the outside, i.e., in thedirection away from the fan wheel 3, in its zero position. Thisoff-center positioning of the rotor 16 relative to the stator 17 has theresult that during a current feed the drive shaft 5 with the rotorarranged on it is drawn in the “down” direction. In addition, an actionof force takes place on the drive shaft 5 by the rotation of the fanwheel 3 in the same direction so that during operation forces actexclusively downward. Therefore, an oscillation of the system of fanwheel 3 and drive shaft 5 is avoided.

A rectangular guide plate 18 is schematically shown on a holder 28 onthe motor mounting 7. The guide plate 18 is offset radially to the sideby the length X2 relative to the drive shaft 5. Radially offsetsignifies in this connection nothing more than a lateral arrangement ofthe guide plate 18 relative to the motor mounting 7 and to theelectromotor 6 fastened on it. Furthermore, the arrangement of the guideplate 18 is selected in such a manner that when the gas fan 1 is beingused in the vertical position (FIG. 1 shows the horizontal position) theguide plate 18 is arranged underneath the electromotor 6 so that a heatflow produced during the operation by the electromotor 6 takes placeupward in the opposite direction of the arrangement of the guide plate18. All structural components outside of the fan housing 2 are coveredby a motor protection cap 19 that has a circumferential edge 20 thatrests on the fan housing 2. Furthermore, the motor protection cap 19 isfastened on the fan housing 2 and therefore decoupled from oscillationsof the electromotor 6. The arrangement of the motor protection cap 19therefore takes place without a gap opposite the fan housing 2. An airconduction conduit 27 is formed inside the motor protection cap 19 whichmakes possible a rapid removal of the heat to the outside. The view ofthe air conduction conduit 27 is only schematic.

FIG. 3 shows a few structural components of the embodiment of FIG. 1 inan exploded view in order to illustrate that the mounting of thestructural components takes place from one side, wherein the details areshown in a simplified manner. The elastomeric element 9 is placed on thefan housing 2 and coupled into it on its circumferential edge 10,wherein stop means 29 are provided which make an alignment of thestructural components relative to each other possible. The motormounting 7 is pushed by the elastomeric element 9 into the interior ofthe fan housing 2 and fixed there with the safety ring 26 to theelastomeric element 9. The ball bearing 13 is inserted into the motormounting 7 and the drive shaft 5 pressed on. Alternatively, the ballbearing 13 can also be pressed onto the drive shaft 5 first and bothparts are introduced together into the motor mounting 7. The structuralcomponents shown further outside (further removed from the housing) inFIG. 1 are omitted in FIG. 3.

The design of the invention is not limited to the previously indicatedpreferred exemplary embodiments but rather a plurality of variants isconceivable which make use of the solution shown even in the case ofembodiments which are basically differently designed. For example, thefan housing can form a base in the area of the through opening on whichthe elastomeric element and the motor mounting rest.

What is claimed is:
 1. A centrifugal fan, in particular a gas fan (1),the centrifugal fan comprising: a fan housing with a fan wheel arrangedin the fan housing, the fan housing defining a through opening forrunning a drive shaft through to be connected to the fan wheel, whereinan electromotor is arranged on an outside of the fan housing and held bya motor mounting, a part of the motor mounting extends through thethrough opening into an interior of the fan housing and the motormounting lies on an elastomeric element arranged on the through openingbetween the fan housing and the motor mounting and is fixed by theelastomeric element on the fan housing.
 2. The centrifugal fan accordingto claim 1, wherein the elastomeric element is constructed as a seal ofthe motor mounting opposite an edge of the through opening of the fanhousing and is arranged directly between the fan housing and the motormounting.
 3. The centrifugal fan according to claim 1, wherein a sealingtest edge running circumferentially on the outside is provided on themotor mounting.
 4. The centrifugal fan according to claim 1, wherein thepart of the motor mounting extending into the interior of the fanhousing extends into a free space provided on the fan wheel or a hub ofthe fan wheel.
 5. The centrifugal fan according to claim 1, wherein thedrive shaft is supported by a ball bearing and a sliding bearing in themotor mounting.
 6. The centrifugal fan according to claim 5, wherein themotor mounting comprises a holder on which the ball bearing rests. 7.The centrifugal fan according to claim 5, wherein a rotor of theelectromotor is arranged between the ball bearing and the slidingbearing and that the ball bearing is located axially on the inner side,i.e., closer to the fan wheel.
 8. The centrifugal fan according to claim1, wherein the electromotor is a direct current motor.
 9. Thecentrifugal fan according to claim 8, wherein a rotor of the directcurrent motor is fastened on the drive shaft and a position of the rotoropposite a stator of the direct current motor is offset by apredetermined axial length from a zero position to an outside, i.e., ina direction away from the fan wheel.
 10. The centrifugal fan accordingto claim 1, wherein a rectangular guide plate is provided to control theelectromotor.
 11. The centrifugal fan according to claim 10, wherein theguide plate can be fastened on the motor mounting radially offset fromthe drive shaft by a length.
 12. The centrifugal fan according to claim11, wherein the guide plate is arranged on the motor mounting in aposition to a side of or below the electromotor and is not influenced bya heat flow caused by the operation of the electromotor.
 13. Thecentrifugal fan according to claim 10, wherein a motor protection capwith a circumferential edge is provided that covers at least theelectromotor, the guide plate and the motor mounting and rests with acircumferential edge on the fan housing.
 14. The centrifugal fanaccording to claim 13, wherein the motor protection cap is fasteneddirectly on the fan housing.
 15. The centrifugal fan according to claim1, wherein at least one air conduction conduit is injected into themotor protection cap.